Current transformer, photovoltaic inverter and photovoltaic system

Abstract

The embodiment of the invention provides a current transformer, a photovoltaic inverter comprising the current transformer and a photovoltaic system comprising the photovoltaic inverter, and relates to the technical field of current transformers. The photovoltaic inverter comprises a circuit board and a current transformer, and the circuit board is provided with a first circuit used for DC arc discharge detection and a second circuit used for power line carrier communication. The current transformer comprises a magnetic core and windings wound on the magnetic core, the windings comprise a first primary winding, a first secondary winding and a second secondary winding, the first primary winding is used for being electrically connected with at least one group of photovoltaic group strings, and the first secondary winding and the second secondary winding are electrically connected with the first circuit and the second circuit respectively. At least two functions can be achieved through one magnetic core, arc discharge detection and communication control over the photovoltaic string are effectively completed, the size of the current transformer is reduced, and the production and manufacturing cost is reduced.

Description

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on February 7, 2024, with application number 202410176989.5 and application name “Current transformer, photovoltaic inverter and photovoltaic system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of current transformers, and in particular to a current transformer, a photovoltaic inverter, and a photovoltaic system. Background Art

[0003] In photovoltaic systems, DC arcing can easily occur in photovoltaic strings due to loose connectors, poor contact, damp wires, or cracked insulation. Electrical fires are often caused by DC arcing. AFCI technology in photovoltaic systems can prevent fires caused by arcing. Furthermore, to improve power generation efficiency, manageability, and safety, power control and monitoring of photovoltaic panels is a major trend in photovoltaic system development. Monitoring of photovoltaic panels is often done only through DC power lines, without dedicated communication lines. Therefore, Power Line Carrier (PLC) communication technology is widely used in photovoltaic systems.

[0004] In related technologies, DC arc detection and power line carrier communication in photovoltaic inverters sample the input current of photovoltaic strings through independent current transformers (CTs) or magnetic rings. However, two independent current transformers occupy a large area on the circuit board and also occupy a large volume within the photovoltaic inverter. Summary of the Invention

[0005] The present application provides a current transformer, a photovoltaic inverter including the current transformer, and a photovoltaic system including the photovoltaic inverter. At least two functions can be realized through a magnetic core, effectively completing arc detection and communication control of photovoltaic strings, reducing the volume of the current transformer, and reducing production and manufacturing costs.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect of the present application, a photovoltaic inverter is provided, comprising a circuit board and a current transformer, wherein a first circuit for DC arc detection and a second circuit for power line carrier communication are provided on the circuit board; the current transformer is arranged on the circuit board, the current transformer comprises a magnetic core and a winding wound on the magnetic core, the winding comprises a first primary winding, a second primary winding, a first secondary winding and a second secondary winding, the first primary winding is used to be electrically connected to the positive end of at least one group of photovoltaic strings, and the second primary winding is used to be electrically connected to the negative end of at least one group of photovoltaic strings, each group of photovoltaic strings comprises at least one photovoltaic module; one of the first secondary winding and the second secondary winding is electrically connected to the first circuit, and the other is electrically connected to the second circuit.

[0008] When current flows through the first and second primary windings, the magnetic core induces current in the first and second secondary windings. One path of the current in the first and second secondary windings is fed back to a first circuit for DC arc detection for analysis, where it is analyzed based on spectral characteristics to determine whether an arc has occurred. The other path is fed back to a second circuit for power line carrier communication, enabling communication with the optimizer or photovoltaic string for control. A single magnetic core can achieve at least two functions, effectively completing both arc detection and communication control for the photovoltaic string. This reduces the footprint of the current transformer, conserves internal space within the photovoltaic inverter, and lowers production and manufacturing costs.

[0009] In addition, the current transformer is usually set close to the cable interface of the photovoltaic inverter (including the positive interface and the negative interface). The first primary winding is electrically connected to the positive end (PV+) of the photovoltaic string, and the second primary winding is electrically connected to the negative end (PV-) of the photovoltaic string. This allows the current at the positive and negative interfaces to be detected for DC arcing before being filtered or passing through other devices, making the results of DC arc detection more accurate.

[0010] In an optional embodiment, the magnetic core is provided with a first winding hole, and the first primary winding, the second primary winding, the first secondary winding and the second secondary winding are all wound at the first winding hole. When the first primary winding and the second primary winding conduct common mode current, the magnetic flux generated by the second primary winding in the magnetic core is opposite to the direction of the magnetic flux generated by the first primary winding in the magnetic core.

[0011] Common-mode current is an inherent characteristic of photovoltaic systems. High-frequency common-mode current not only increases system losses and generates grid-connected current harmonics, but also causes electromagnetic interference and other problems, and can even threaten personal safety. To suppress common-mode current, at least a portion (partially or entirely) of the second primary winding is positioned within the first winding hole. When current is applied, the first and second primary windings conduct differential-mode current, causing the second and first primary windings to generate magnetic flux in the same direction on the magnetic core. This allows the common-mode current to flow through the first and second primary windings, generating magnetic flux in opposite directions on the magnetic core. This allows the magnetic flux generated by the common-mode current on the magnetic core to at least partially cancel each other out, thereby suppressing the common-mode current, reducing the possibility of common-mode current interfering with other components, and improving the system's electromagnetic compatibility (EMC).

[0012] In an optional embodiment, the magnetic core includes a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column, the second magnetic column and the third magnetic column are arranged along the extension direction of the first magnetic column, the second magnetic column and the third magnetic column are located on the same side of the first magnetic column, the fourth magnetic column is located on the side of the second magnetic column away from the first magnetic column, the fourth magnetic column extends from the second magnetic column to the third magnetic column, and the first magnetic column, the second magnetic column, the third magnetic column and the fourth magnetic column form a first winding hole.

[0013] The first, second, third, and fourth magnetic pillars form a magnetic core (shaped like a "U"), enclosing a first winding hole to facilitate winding on the core. Furthermore, multiple magnetic pillars can be spliced, connected, and assembled as needed, allowing the core to form a variety of shapes and types to suit the assembly requirements of photovoltaic inverters.

[0014] In an optional embodiment, the magnetic core includes a first winding hole and a second winding hole, and a middle column located between the first winding hole and the second winding hole, a first air gap is provided at other positions of the part of the magnetic core surrounding the first winding hole except the middle column, and a second air gap is provided at other positions of the part of the magnetic core surrounding the second winding hole except the middle column; a first primary winding and a first secondary winding are wound around the first winding hole, and a second secondary winding and at least part of the second primary winding are wound around the second winding hole.

[0015] The first primary winding and the first secondary winding both pass through the first winding hole, corresponding to each other. When current flows through the first primary winding, current is induced in the first secondary winding through the magnetic core. The portion of the second primary winding that passes through the second winding hole corresponds to the second secondary winding. When current flows through the second primary winding, current is induced in the second secondary winding through the magnetic core. Furthermore, the first and second air gaps are located on different sides of the center column. The portion of the magnetic core with an air gap (the first or second air gap) has a higher magnetic resistance. The center column of the magnetic core has no air gap and very low magnetic resistance. Therefore, the magnetic circuits (the closed paths through which the magnetic flux passes) on both sides preferentially close at the center column. For example, after current is loaded, the first primary winding forms a first magnetic circuit in the magnetic core, and the part of the second primary winding passing through the second winding hole forms a second magnetic circuit in the magnetic core. The first magnetic circuit and the second magnetic circuit are preferentially closed at the center column, thereby realizing mutual decoupling of the two magnetic circuits, reducing the possibility of mutual influence or interference between the two magnetic circuits, and enabling the two functions of DC arc detection and power line carrier communication to be independently realized and the dual functions to be independently controlled.

[0016] In an optional embodiment, when the first primary winding and the second primary winding conduct differential mode current, the magnetic flux generated by the part of the second primary winding wound around the second winding hole in the center column is opposite in direction to the magnetic flux generated by the first primary winding in the center column.

[0017] When current is loaded, when the first primary winding and the second primary winding conduct differential mode current, the magnetic flux directions of the first magnetic circuit and the second magnetic circuit on the center column are opposite, and the magnetic fluxes cancel each other out, making the impedance on the center column smaller (if the magnetic fluxes are superimposed, a larger impedance will be generated), so that the first magnetic circuit and the second magnetic circuit are preferentially closed in the center column, which is beneficial to the mutual decoupling of the first magnetic circuit and the second magnetic circuit, and reduces the possibility of mutual influence and interference between the first magnetic circuit and the second magnetic circuit.

[0018] In an optional embodiment, a portion of the second primary winding is wound at the first winding hole, and another portion of the second primary winding is wound at the second winding hole; when the first primary winding and the second primary winding conduct common mode current, the magnetic flux generated in the magnetic core by the portion of the second primary winding wound at the first winding hole is in the opposite direction to the magnetic flux generated in the magnetic core by the first primary winding.

[0019] When current is loaded, when the first primary winding and the second primary winding conduct differential mode current, the part of the second primary winding passing through the first winding hole and the first primary winding respectively generate magnetic fluxes in the same direction on the magnetic core. In this way, when the common mode current flows through the first primary winding and the second primary winding, magnetic fluxes in opposite directions are respectively generated on the magnetic core, so that the magnetic fluxes generated by the common mode current on the magnetic core can at least partially offset each other, thereby suppressing the common mode current, reducing the possibility of the common mode current interfering with other devices, and improving the electromagnetic compatibility of the system.

[0020] In an optional embodiment, a third circuit is provided on the circuit board, and the third circuit is used to test the first circuit. The current transformer also includes a third secondary winding arranged at the first winding hole, the first secondary winding is electrically connected to the first circuit, and the third secondary winding is electrically connected to the third circuit.

[0021] A third circuit (e.g., a self-test circuit) is provided on the circuit board. When current flows through the first primary winding, the current induced by the third secondary winding is fed back to the third circuit to detect whether the first circuit (the circuit for DC arc detection) is operating normally, thereby determining the accuracy of arc detection by the first circuit. If the third circuit detects that the first circuit is operating normally, the current induced by the first secondary winding is fed back to the first circuit for analysis, thereby obtaining an accurate result.

[0022] In an optional embodiment, the magnetic core also includes a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column, the second magnetic column and the third magnetic column are arranged along the extension direction of the first magnetic column, the middle column is located between the second magnetic column and the third magnetic column, the fourth magnetic column is located on the side of the middle column away from the first magnetic column, the fourth magnetic column extends from the second magnetic column to the third magnetic column, the first winding hole is located between the second magnetic column and the middle column, and the second winding hole is located between the third magnetic column and the middle column.

[0023] The magnetic core (shaped like a "sun") is formed by the first, second, third, and fourth magnetic columns, along with the center column. First and second winding holes are formed to facilitate winding on the core. Furthermore, multiple magnetic columns can be spliced, connected, and assembled as needed, creating a variety of core shapes and types to suit the assembly requirements of photovoltaic inverters.

[0024] In an optional embodiment, the second magnetic column, the third magnetic column and the middle column are all connected to the same side of the first magnetic column, the middle column is in contact with the fourth magnetic column, a first air gap is formed between the second magnetic column and the fourth magnetic column, and a second air gap is formed between the third magnetic column and the fourth magnetic column.

[0025] Through the above design method, the magnetic core can be made into an EI type, that is, the first magnetic column, the second magnetic column, the third magnetic column and the middle column constitute an E-type magnetic core, and the fourth magnetic column is an I-type magnetic core. It is only necessary to reserve air gaps between the second magnetic column and the fourth magnetic column and between the third magnetic column and the fourth magnetic column, which facilitates the production and manufacturing of the magnetic core.

[0026] In an optional implementation, the first primary winding and the second primary winding are both wound on a fourth magnetic column, and the fourth magnetic column is located on a side of the first magnetic column facing the circuit board.

[0027] The primary windings (the first primary winding and the second primary winding) and the secondary windings (the first secondary winding and the second secondary winding) are all wound on the same magnetic column (the fourth magnetic column), that is, the primary windings and the secondary windings are located on the same side of the magnetic core and are arranged close to the circuit board, which facilitates the connection of the primary windings and the secondary windings to the circuit board.

[0028] In an optional embodiment, the current transformer also includes a first insulating sleeve mounted on the magnetic core, the first insulating sleeve passes through the first winding hole, the first secondary winding is wound outside the first insulating sleeve, the first primary winding is wound around the periphery of the first secondary winding, and insulating tape is arranged between the first primary winding and the first secondary winding. The current transformer also includes a second insulating sleeve mounted on the magnetic core, the second insulating sleeve passes through the second winding hole, the second secondary winding is wound outside the second insulating sleeve, the part of the second primary winding passing through the second winding hole is wound around the periphery of the second secondary winding, and insulating tape is arranged between the second primary winding and the second secondary winding.

[0029] The secondary winding is wound at the corresponding position of the magnetic core. For example, the first secondary winding is wound outside the first insulating sleeve, and the second secondary winding is wound outside the second insulating sleeve. Then, the primary winding is wound around the corresponding secondary winding. For example, the first primary winding is wound around the first secondary winding, and the portion of the second primary winding that passes through the second winding hole is wound around the second secondary winding. Insulating tape is placed between the primary winding and the corresponding secondary winding. For example, after the secondary winding is wound, it is wrapped with insulating tape first, and then the primary winding is wound. This can insulate the primary winding from the secondary winding.

[0030] In an optional embodiment, the current transformer also includes an insulating bracket, which is arranged on a circuit board. A support block is provided on the insulating bracket, which supports the magnetic core. There is a gap between the magnetic core and the insulating bracket. A plurality of through openings are provided on the insulating bracket, and the two ends of the first primary winding and the two ends of the second primary winding respectively pass through the corresponding through openings and are electrically connected to the circuit board.

[0031] The insulating bracket is mounted on the circuit board, and the support block supports the magnetic core, ensuring a gap between the core and the insulating bracket for easier winding. The insulating bracket is provided with multiple openings, through which the ends of the first and second primary windings pass, respectively. The ends of the primary windings extend to the bottom of the insulating bracket, facilitating connection to the circuit board.

[0032] In an optional embodiment, multiple groups of photovoltaic strings are provided, the first primary winding includes multiple first coils, the multiple first coils are arranged at intervals, each first coil is electrically connected to the positive end of a corresponding group of photovoltaic strings, and the second primary winding includes a second coil, the cross-sectional area of the second coil is larger than the cross-sectional area of a single first coil, and the second coil is used to be electrically connected to the negative ends of multiple groups of photovoltaic strings.

[0033] A photovoltaic system can include multiple photovoltaic strings, which serve as the input source for a photovoltaic inverter. The positive and negative terminals of each photovoltaic string are electrically connected to the photovoltaic inverter, inputting current into the inverter. The first primary winding includes multiple first coils, each of which can be electrically connected to the positive terminal of a photovoltaic string to prevent short circuits among the multiple photovoltaic strings. The current input to the photovoltaic inverter flows to the second coil of the second primary winding and then returns to the negative terminal of the photovoltaic string, forming a loop. This ensures that the total current flowing through the multiple first coils is equal to the current flowing through the second coil. Furthermore, this design is more suitable for the wiring requirements of the photovoltaic inverter circuit board.

[0034] In an optional embodiment, the number of turns of the plurality of first coils is the same, and the number of turns of any one of the first coils is equal to the number of turns of the second coil wound around the first winding hole.

[0035] When common-mode current flows through the first primary winding and the second primary winding, magnetic fluxes with opposite directions are generated on the magnetic core respectively. When the number of turns of the second coil at the first winding hole is equal to the number of turns of the single first coil, the common-mode current flowing through the first primary winding and the second primary winding will generate magnetic fluxes of equal magnitude on the magnetic core respectively, so that the magnetic fluxes generated by the common-mode current on the magnetic core cancel each other out, reducing the possibility of common-mode current interfering with other devices.

[0036] In an optional embodiment, the portion where the second coil is wound around the first winding hole is arranged in the middle of the first winding hole, and at least one first coil is arranged on both sides of the portion where the second coil is wound around the first winding hole, and the two first coils adjacent to the portion where the second coil is wound around the first winding hole are equidistant from the portion where the second coil is wound around the first winding hole.

[0037] The coil is designed to be close to the middle of the winding hole, which can reduce leakage magnetic flux. Since the current flowing through the second coil is relatively large, the second coil can be set in the middle of the first winding hole. In addition, in order to reduce the leakage magnetic flux of the first coil, multiple first coils are set as close as possible to the middle of the first winding hole, and multiple first coils can be distributed on both sides of the part where the second coil is wound around the first winding hole, and as close as possible to the second coil. However, there are distance requirements between the first coil and the second coil. In this case, when the minimum spacing is met, the distance from the first coil to the second coil on both sides is the same, or a symmetrical design is adopted. In this way, leakage inductance can be reduced, which also reduces the impact on the accuracy of the detection signal amplitude.

[0038] In a second aspect of the present application, a current transformer is provided, comprising a magnetic core and a winding wound on the magnetic core, the winding comprising a first primary winding, a second primary winding, a first secondary winding and a second secondary winding, the first primary winding being used to be electrically connected to the positive terminal of a power supply, the second primary winding being used to be electrically connected to the negative terminal of the power supply, the first secondary winding being used to be electrically connected to a circuit for DC arc detection, and the second secondary winding being used to be electrically connected to a circuit for power line carrier communication.

[0039] The current induced in the first secondary winding and the current induced in the second secondary winding are fed back to different circuits, respectively. A single magnetic core can achieve at least two functions, reducing the size and board area of the current transformer and lowering production and manufacturing costs.

[0040] In an optional embodiment, the magnetic core is provided with a first winding hole, and the first primary winding, the second primary winding, the first secondary winding and the second secondary winding are all wound at the first winding hole. When the first primary winding and the second primary winding conduct common mode current, the magnetic flux generated by the second primary winding in the magnetic core is opposite to the direction of the magnetic flux generated by the first primary winding in the magnetic core.

[0041] When the common-mode current flows through the first primary winding and the second primary winding, magnetic fluxes in opposite directions are generated in the magnetic core respectively. The magnetic fluxes generated by the common-mode current on the magnetic core at least partially cancel each other out, thereby suppressing the common-mode current, reducing the possibility of the common-mode current interfering with other devices, and improving the electromagnetic compatibility of the system.

[0042] In an optional embodiment, the magnetic core includes a first winding hole and a second winding hole, and a middle column located between the first winding hole and the second winding hole, a first air gap is provided at other positions of the part of the magnetic core surrounding the first winding hole except the middle column, and a second air gap is provided at other positions of the part of the magnetic core surrounding the second winding hole except the middle column; a first primary winding and a first secondary winding are wound around the first winding hole, and a second secondary winding and at least part of the second primary winding are wound around the second winding hole.

[0043] The first primary winding and the first secondary winding both pass through the first winding hole. The first primary winding and the first secondary winding correspond to each other. When current flows through the first primary winding, current is induced in the first secondary winding through the magnetic core. The portion of the second primary winding that passes through the second winding hole corresponds to the second secondary winding. When current flows through the second primary winding, current is induced in the second secondary winding through the magnetic core. In addition, the first air gap and the second air gap are located on either side of the center column. The center column of the magnetic core has no air gap, and the magnetic resistance is very small. The magnetic circuits on both sides will preferentially close at the center column, achieving decoupling of the two magnetic circuits and reducing the possibility of mutual influence between the two magnetic circuits. At least two functions can be achieved through a single magnetic core, reducing the board area occupied by the current transformer and saving internal space in the photovoltaic inverter.

[0044] In an optional embodiment, when the first primary winding and the second primary winding conduct differential mode current, the magnetic flux generated by the part of the second primary winding wound around the second winding hole in the center column is opposite in direction to the magnetic flux generated by the first primary winding in the center column.

[0045] When current is loaded, the magnetic flux directions of the first magnetic circuit and the second magnetic circuit on the middle column are opposite, making the impedance on the middle column smaller (if the magnetic flux is superimposed, a larger impedance will be generated), so that the first magnetic circuit and the second magnetic circuit are closed on the middle column first, which is conducive to the decoupling of the two magnetic circuits and reduces the possibility of mutual influence between the two magnetic circuits.

[0046] In an optional embodiment, the magnetic core also includes a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column, the second magnetic column and the third magnetic column are distributed along the extension direction of the first magnetic column, the middle column is located between the second magnetic column and the third magnetic column, the fourth magnetic column is located on the side of the middle column away from the first magnetic column, the fourth magnetic column extends from the second magnetic column to the third magnetic column, the second magnetic column, the third magnetic column and the middle column are all connected to the same side of the first magnetic column, the middle column is in contact with the fourth magnetic column, a first air gap is formed between the second magnetic column and the fourth magnetic column, and a second air gap is formed between the third magnetic column and the fourth magnetic column.

[0047] Through the above design method, the magnetic core of the current transformer can be made into an EI type, that is, the first magnetic column, the second magnetic column, the third magnetic column and the middle column constitute an E-type magnetic core, and the fourth magnetic column is an I-type magnetic core. It is only necessary to set air gaps between the second magnetic column and the fourth magnetic column and between the third magnetic column and the fourth magnetic column, which facilitates the production and manufacturing of the magnetic core.

[0048] In an optional embodiment, the first primary winding includes multiple first coils, which are arranged at intervals, and the second primary winding includes a second coil, the cross-sectional area of the second coil is larger than the cross-sectional area of the single first coil, and when current is loaded, the sum of the currents flowing through the multiple first coils is equal to the current flowing through the second coil.

[0049] The current transformer may be electrically connected to multiple input sources. The first primary winding includes multiple first coils that are not connected to each other. Each first coil can be electrically connected to one input source to avoid short circuit of multiple input sources.

[0050] In an optional embodiment, the number of turns of the plurality of first coils is the same, and the number of turns of the portion of the second coil wound around the first winding hole is equal to the number of turns of each first coil.

[0051] When the common-mode current flows through the first primary winding and the second primary winding, magnetic fluxes of equal magnitude and opposite directions are generated on the magnetic core respectively, so that the magnetic fluxes generated by the common-mode current on the magnetic core cancel each other out, reducing the possibility of the common-mode current interfering with other devices.

[0052] In a third aspect of the present application, a photovoltaic system is provided, comprising at least one optimizer and the above-mentioned photovoltaic inverter, each optimizer being used to be connected to at least one photovoltaic component; and at least one optimizer being electrically connected to the second circuit of the photovoltaic inverter.

[0053] The photovoltaic string can be used as the input source of the photovoltaic inverter. The positive terminal and the negative terminal of each photovoltaic string are electrically connected to the photovoltaic inverter respectively, and current is input to the photovoltaic inverter. Information is transmitted between the photovoltaic inverter and the optimizer through power line carrier communication (PLC), that is, the photovoltaic inverter and the optimizer are connected by a power cable, and information is transmitted through the second circuit (a circuit for power line carrier communication) and the power cable, including information interaction operations such as business query and command control. In addition, the photovoltaic system provided by this application includes the above-mentioned photovoltaic inverter, so the photovoltaic system provided by this application and the photovoltaic inverter of the above-mentioned technical solution can solve the same technical problems and have the same technical effects, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A schematic diagram of a partial structure of a photovoltaic system provided in an embodiment of the present application;

[0055] Figure 2 A schematic diagram of a connection method of an optimizer provided in an embodiment of the present application;

[0056] Figure 3 A schematic diagram of another connection method of an optimizer provided in an embodiment of the present application;

[0057] Figure 4 A schematic diagram of a partial structure of a photovoltaic inverter provided in an embodiment of the present application;

[0058] Figure 5 A schematic diagram of a partial structure of a current transformer provided in an embodiment of the present application;

[0059] Figure 6 A schematic diagram of the distance between the first coil and the second coil provided in an embodiment of the present application;

[0060] Figure 7 A schematic diagram of a current transformer provided in an embodiment of the present application;

[0061] Figure 8 A current flow diagram of the first coil and the second coil provided in an embodiment of the present application;

[0062] Figure 9 A magnetic circuit direction diagram of the first coil and the second coil when a normal current is loaded according to an embodiment of the present application;

[0063] Figure 10A current flow diagram of common-mode current on the first coil and the second coil provided in an embodiment of the present application;

[0064] Figure 11 A magnetic circuit direction diagram when a common-mode current flows through a first coil and a second coil according to an embodiment of the present application;

[0065] Figure 12 A schematic diagram of a partial structure of another photovoltaic inverter provided in an embodiment of the present application;

[0066] Figure 13 Schematic diagram of the structures of various magnetic cores provided in the embodiments of the present application;

[0067] Figure 14 A schematic diagram of a first magnetic circuit and a second magnetic circuit provided in an embodiment of the present application;

[0068] Figure 15 A schematic structural diagram of a first primary winding and a second primary winding provided in an embodiment of the present application;

[0069] Figure 16 A schematic structural diagram of a first secondary winding, a second secondary winding, and a third secondary winding provided in an embodiment of the present application;

[0070] Figure 17 A schematic diagram of a partial structure of another current transformer provided in an embodiment of the present application;

[0071] Figure 18 A schematic structural diagram of a through opening of an insulating bracket provided in an embodiment of the present application;

[0072] Figure 19 A schematic diagram of another current transformer provided in an embodiment of the present application;

[0073] Figure 20 A schematic structural diagram of a magnetic core of another current transformer provided in an embodiment of the present application.

[0074] Reference numerals:

[0075] 100- Photovoltaic system;

[0076] 200-PV string; 201-PV module; 202-optimizer; 203-conductor; 204-power cable;

[0077] 300-photovoltaic inverter; 301-circuit board; 302-current transformer;

[0078] 1-magnetic core; 101-first winding hole; 102-second winding hole; 103-air gap; 1031-first air gap; 1032-second air gap; 1033-third air gap; 11-first magnetic column; 12-second magnetic column; 13-third magnetic column; 14-fourth magnetic column; 15-middle column;

[0079] 21-first primary winding; 211-first coil; 22-second primary winding; 220-second coil; 221-first part; 222-second part; 223-third part;

[0080] 31-first secondary winding; 32-second secondary winding; 33-third secondary winding;

[0081] 4-first insulating sleeve; 41-groove; 42-first pin;

[0082] 5-second insulating sleeve; 51-second plug pin;

[0083] 6-pin;

[0084] 7-Insulation tape;

[0085] 8-insulating bracket; 81-support block; 82-through port; 83-socket. DETAILED DESCRIPTION

[0086] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0087] In this application, the terms "first," "second," etc., are used solely for descriptive purposes to distinguish one element from another and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of such features. Furthermore, in this application, unless otherwise expressly specified or limited, "plurality" means two or more.

[0088] In this application, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; they can refer to direct connection, indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0089] In this application, unless otherwise expressly specified and limited, the term "coupling" should be understood in a broad sense. For example, "coupling" can be a direct electrical connection between two components, for example, physical contact and electrical conduction between two components. It can also be understood as the electrical connection between different components in the circuit structure through a physical line that can transmit electrical signals, such as printed circuit board (PCB) copper foil or wire, to transmit electrical signals; or, "coupling" can be an indirect electrical connection between two components through an intermediate medium; or, "coupling" can be an electrical connection between two components in an air-spaced / non-contact manner, for example, two components are electrically connected by capacitive coupling, inductive coupling or resistive coupling to transmit electrical signals. In addition, in the embodiments of the present application, the term "decoupling" means that there is no direct or indirect electrical connection relationship between two components, so no electrical signal will be transmitted between the two decoupled components.

[0090] Furthermore, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described in this application as "exemplary" or "for example" should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0091] In the drawings of the embodiments of the present application, physical structures such as components and assemblies are represented by guide lines; hollow structures such as openings, holes, spaces, and cavities are represented by guide lines with arrows.

[0092] In the photovoltaic system 100, distributed photovoltaic power generation is one of the main forms and has broad application prospects. Figure 1 , attached Figure 1 The structure of the photovoltaic system 100 is shown as an example, wherein the photovoltaic system 100 may include at least one set of photovoltaic strings 200 and a photovoltaic inverter 300. Figure 1 In the illustrated example, the photovoltaic system 100 includes a plurality of photovoltaic strings 200 . In other examples, only one photovoltaic string 200 is provided in the photovoltaic system 100 .

[0093] Reference Figure 1Each photovoltaic string 200 includes a plurality of photovoltaic modules 201 (e.g., photovoltaic panels), and the plurality of photovoltaic modules 201 in each photovoltaic string 200 are connected in series. In other examples, the plurality of photovoltaic modules 201 in each photovoltaic string 200 can be connected in parallel; in other examples, the plurality of photovoltaic modules 201 in each photovoltaic string 200 can be partially connected in series and partially connected in parallel. The photovoltaic modules 201 are used to convert solar energy into electrical energy (generally direct current), and the photovoltaic modules 201 are greatly affected by light radiation. For example, if there is an obstruction blocking the photovoltaic module 201, the power generation of the obscured photovoltaic module 201 will be significantly reduced.

[0094] In order to improve power generation efficiency and enhance system reliability, the photovoltaic system 100 may further include at least one optimizer 202 . Figure 2 An exemplary connection method of an optimizer 202 is shown. In this example, an optimizer 202 (photovoltaic power optimizer) is provided on each photovoltaic module 201 in each photovoltaic string 200. The positive pole of the input side of each optimizer 202 is connected to the negative pole of the corresponding photovoltaic module 201 through a wire 203. The negative pole of the input side of each optimizer 202 is connected to the positive pole of the corresponding photovoltaic module 201 through a wire 203. The output sides of multiple optimizers 202 in each photovoltaic string 200 are connected in series through power cables 204. That is, multiple optimizers 202 corresponding to multiple photovoltaic modules 201 in each photovoltaic string 200 are connected in series through power cables 204 and connected to the photovoltaic inverter 300 (auxiliary reference). Figure 1 ).

[0095] Figure 3 Another connection mode of the optimizer 202 is shown as an example. In this example, multiple photovoltaic modules 201 in each photovoltaic string 200 can share one optimizer 202. Figure 3 In each photovoltaic string 200, two photovoltaic modules 201 are connected to one optimizer 202, the positive pole on the input side of each optimizer 202 is connected to the negative pole of one of the corresponding two photovoltaic modules 201 through a wire 203, the negative pole on the input side of each optimizer 202 is connected to the positive pole of another photovoltaic module 201 through a wire 203, the positive and negative poles of the two photovoltaic modules 201 connected to the same optimizer 202 are connected through a wire 203, and the output sides of multiple optimizers 202 in each photovoltaic string 200 are connected in series through power cables 204.

[0096] It should be noted that the power cable 204 of the present application may include multiple cables, some cables are used to connect two adjacent optimizers 202 or to connect two adjacent photovoltaic components 201, and some cables are used to connect the optimizer 202 and the photovoltaic inverter 300, or to connect the photovoltaic component 201 and the photovoltaic inverter 300.

[0097] Among them, the optimizer 202 is a device for converting the direct current generated by the photovoltaic component 201 into adjustable direct current, that is, the direct current output by the photovoltaic component 201 is converted from DC to DC and output as direct current with adjustable voltage and current, which is used to realize dynamic control of the direct current generated by the photovoltaic component 201.

[0098] For example, when there is an obstruction, the output power of a certain photovoltaic module 201 (the obstructed photovoltaic module 201) in the photovoltaic string 200 may become unstable. Without the optimizer 202, the current value of the entire photovoltaic string 200 on the power cable 204 will be pulled down to the current value output by the obstructed photovoltaic module 201 (the minimum current value), resulting in a waste of resources. The optimizer 202 can balance the output power of each photovoltaic module 201, so that the overall output power on the power cable 204 is stable. In addition, the optimizer 202 can also shut down the output of the corresponding connected photovoltaic module 201 in an emergency to reduce safety hazards.

[0099] Each photovoltaic string 200 is connected to a photovoltaic inverter 300 via power cables 204. Both the positive terminal (PV+) and the negative terminal (PV-) of each photovoltaic string 200 are connected to the photovoltaic inverter 300. That is, the power cables 204 at the positive terminal (PV+) and the power cables 204 at the negative terminal (PV-) are connected to the connection terminals (or cable interfaces) of the photovoltaic inverter 300, providing the input source for the photovoltaic inverter 300. The photovoltaic inverter 300 can convert the variable direct current (DC) generated by the photovoltaic modules 201 into AC power at a mains frequency, which can be fed back to the commercial power transmission system or used by an off-grid power grid.

[0100] In order to improve power generation efficiency, manageability and safety, power control and monitoring of photovoltaic modules 201 is a major trend in photovoltaic development. Photovoltaic modules 201 are connected to DC power cables 204 and have no separate communication lines. Therefore, power line carrier (PLC) communication technology is widely used in photovoltaic systems 100.

[0101] Power line carrier communication (PLC), also known as power line communication, carrier communication, or PLC communication, refers to a specialized communication method that uses power cables 204 as an information transmission medium for voice or data transmission. In other words, PLC essentially modulates network signals (also known as PLC signals) onto power cables 204, utilizing existing power cables 204 to address network cabling issues.

[0102] The PV inverter 300 and optimizer 202 are connected via power cable 204, which transmits information (including information exchange operations such as service queries and command control) through power cable 204. This allows the PV inverter 300 to communicate with the optimizer 202 using PLC communication technology. The PV inverter 300 sends PLC signals to the power cable 204, or receives PLC signals from the power cable 204.

[0103] For example, the photovoltaic inverter 300 collects signals on the power cable 204. By analyzing the signals, it can be determined whether the photovoltaic component 201 is blocked, whether the angle of the photovoltaic component 201 is appropriate, etc. By capturing and analyzing these signals, the photovoltaic inverter 300 issues instructions to control the optimizer 202 to achieve maximum power output and online monitoring of the photovoltaic component 201, thereby improving the efficiency of the photovoltaic system 100.

[0104] Furthermore, electrical fires are a risk that distributed photovoltaic systems must mitigate. Arcing can occur in photovoltaic strings 200 due to loose or poor contacts, damp wiring, cracked insulation, or aging cables. Arcing generates high temperatures, which can produce flames if intense. In electrical systems, arcing not only decomposes or carbonizes surrounding insulation, rendering it ineffective, but can also easily cause nearby materials to reach their ignition point and ignite. Because photovoltaic system 100 has numerous DC-side terminals, the potential for arcing is high. DC arc detection technology (AFCI) in photovoltaic system 100 can prevent fires caused by arcing.

[0105] DC arc detection can be performed through the photovoltaic inverter 300. For example, the current signal of the DC side (photovoltaic string 200) of the photovoltaic inverter 300 is first obtained. If the current signal obtained is an analog quantity, the analog current signal needs to be converted into a digital signal; if the current signal obtained is already a digital signal, no further conversion is required. Determine whether the spectral characteristics of the current signal have the spectral characteristics of an arc. For example, the obtained digital signal is subjected to a fast Fourier transform (FFT) to obtain the spectral characteristics of the current signal, and then further determine whether the spectral characteristics of the current signal have the spectral characteristics of an arc. When an arc phenomenon occurs, the arc noise will be superimposed on the basic spectrum of the photovoltaic inverter 300, thereby forming an arc spectrum characteristic.

[0106] In some examples, a predetermined power threshold (set as needed) can be used to determine whether the spectral characteristics of the current signal have spectral characteristics of an arc. For example, if the spectral characteristics of the current signal exceed the predetermined power threshold, it is determined that the spectral characteristics of the current signal have spectral characteristics of an arc, and an arc phenomenon is considered to have occurred. Otherwise, the spectral characteristics of the current signal are considered not to have spectral characteristics of an arc, that is, an arc phenomenon is considered not to have occurred.

[0107] The embodiment of the present application provides a photovoltaic inverter 300, referring to Figure 4 , Figure 4 The following illustrates a partial structure of a photovoltaic inverter 300. The exemplary photovoltaic inverter 300 includes a housing (not shown in the drawings) and a circuit board 301 disposed within the housing. The photovoltaic inverter 300 includes multiple circuits, including a first circuit for DC arc detection and a second circuit for power line carrier communication. Both the first and second circuits are disposed on the circuit board 301. For example, the two circuits (the first and second circuits) may be integrated into a chip disposed on the circuit board 301.

[0108] The first circuit for DC arc detection can condition and analyze the sampled current signal, combining the spectral characteristics to determine whether an arc has occurred, thereby quickly determining and processing whether an arc has occurred in the photovoltaic system 100. For example, the current signal of the photovoltaic string 200 is obtained, and the conditioning circuit (signal processing circuit) converts the analog signal into a digital signal. The spectral characteristics of the current signal are determined to determine whether they have the spectral characteristics of an arc. If an arc is detected, the photovoltaic inverter 300 will issue an alarm, and the photovoltaic inverter 300 and optimizer 202 will stop operating. The staff will check the line condition and perform repairs. After the system returns to normal, it will be powered on again.

[0109] Furthermore, after the sampled current signal is fed back to the second circuit for power line carrier communication, it can be debugged into a digital signal via the PLC carrier. The PV inverter 300 receives the PLC signal from the optimizer 202, or transmits the PLC signal to the power cable 204, enabling effective detection and control of the remote optimizer 202 or PV string 200.

[0110] In order to sample the input current on the power cable 204, refer to Figure 4 The photovoltaic inverter 300 further includes a current transformer 302 , which is disposed on a circuit board 301 .

[0111] The embodiment of the present application provides a current transformer 302, referring to Figure 4The exemplary current transformer 302 includes a magnetic core 1 and a winding, wherein the winding is wound on the magnetic core 1. The magnetic core is provided with a first winding hole 101, and at least part of the winding is wound around the first winding hole 101. The winding around the first winding hole 101 means that the winding is wound around the magnetic column around the first winding hole 101 and passes through the first winding hole 101.

[0112] For example, refer to Figure 4 , the magnetic core 1 may include a first magnetic column 11, a second magnetic column 12, a third magnetic column 13 and a fourth magnetic column 14. The extension directions of the first magnetic column 11 and the fourth magnetic column 14 are parallel. The second magnetic column 12 and the third magnetic column 13 are both located between the first magnetic column 11 and the fourth magnetic column 14. The second magnetic column 12 and the third magnetic column 13 are distributed along the extension direction of the first magnetic column 11. For example, the second magnetic column 12 and the third magnetic column 13 may be located at both ends of the first magnetic column 11. In some examples, the fourth magnetic column 14 extends from the second magnetic column 12 to the third magnetic column 13, that is, the second magnetic column 12 and the third magnetic column 13 may also be located at both ends of the fourth magnetic column 14. Figure 4 In the example shown, the first winding hole 101 may be located between the second magnetic column 12 and the third magnetic column 13 . Furthermore, the winding passing through the first winding hole 101 (or the winding at the first winding hole 101 ) is located between the second magnetic column 12 and the third magnetic column 13 .

[0113] The magnetic core 1 can be a spliced structure, for example, Figure 4 The magnetic core 1 is of CI or UI type, that is, a C-type magnetic core and an I-type magnetic core are spliced together, or a U-type magnetic core and an I-type magnetic core are spliced together, which is conducive to adjusting the magnetic inductance and other performance. In other examples, the magnetic core 1 can also be an SQ core or a toroidal core. In addition, the material of the magnetic core 1 can be any suitable material, such as manganese-zinc ferrite, nickel-zinc ferrite, etc., and this application does not impose specific limitations on this.

[0114] The first winding hole 101 is a through-hole structure formed on the magnetic core 1 . The size of the first winding hole 101 can be set according to the winding situation, and this application does not impose any specific restrictions on this.

[0115] To reduce the possibility of saturation of the magnetic core 1, a gap (or air gap) can be provided on the magnetic core 1. For example, a gap can be provided between the second magnetic column 12 and the fourth magnetic column 14, or a gap can be provided between the third magnetic column 13 and the fourth magnetic column 14. In other examples, when a CI-type or UI-type magnetic core 1 is used, the magnetic core 1 can also be provided without a gap, and this application does not impose specific limitations on this.

[0116] In the present application, the windings of the current transformer 302 may include a primary winding and a secondary winding, and the current on the primary winding may be coupled to the secondary winding through the magnetic core 1 . Figure 5The structure of a primary winding and a secondary winding is shown as an example. Figure 5 The winding may include a first primary winding 21, a first secondary winding 31 and a second secondary winding 32. When current flows through the first primary winding 21, current may be induced in the first secondary winding 31 and the second secondary winding 32 through the magnetic core 1. Figure 5 In the illustrated example, the first primary winding 21 , the first secondary winding 31 , and the second secondary winding 32 all pass through the first winding hole 101 .

[0117] The first primary winding 21 is electrically connected to the positive terminal (PV+) or negative terminal (PV-) of at least one photovoltaic string 200. For example, the first primary winding 21 can be electrically connected to the positive terminal of one photovoltaic string 200 or to the positive terminals of multiple photovoltaic strings 200. For another example, the first primary winding 21 can be electrically connected to the negative terminal of one photovoltaic string 200 or to the negative terminals of multiple photovoltaic strings 200. One of the first secondary winding 31 and the second secondary winding 32 is electrically connected to a first circuit for DC arc detection, and the other is electrically connected to a second circuit for power line carrier communication. In other words, the currents in the first secondary winding 31 and the second secondary winding 32 are fed back to the first circuit for DC arc detection for analysis, where they are combined with spectral characteristics to determine whether an arc has occurred. The currents in the second secondary winding 31 and the second secondary winding 32 are fed back to the second circuit for power line carrier communication, thereby enabling communication control of the remote optimizer 202.

[0118] For example, the first secondary winding 31 is electrically connected to the first circuit, and the second secondary winding 32 is electrically connected to the second circuit. For another example, the second secondary winding 32 is electrically connected to the first circuit, and the first secondary winding 31 is electrically connected to the second circuit.

[0119] In addition, in order to detect whether the first circuit for DC arc detection is operating normally, a third circuit (e.g., a self-test circuit) for testing the first circuit is also provided on the circuit board 301. There are many types of third circuits. For example, the third circuit can be provided with a noise (e.g., arc signal) generating circuit. The noise generating circuit can generate a noise signal with the same spectral characteristics as the arc noise signal. The third circuit can output the noise signal to the first circuit to test whether the first circuit can detect the noise signal, and thereby determine whether the first circuit is functioning normally.

[0120] In order to feed back the current signal to the third circuit, refer to Figure 5The windings may also include a third secondary winding 33 wound around the magnetic core 1. The third secondary winding 33 is electrically connected to the third circuit. When current flows through the first primary winding 21, the third secondary winding 33 feeds the induced current back to the third circuit to test the proper operation of the first circuit for DC arc detection. If the first circuit is operating properly, the current induced by the first secondary winding 31 is fed back to the first circuit for analysis, yielding accurate results.

[0121] In some examples, the first circuit for DC arc detection and the third circuit for detecting the first circuit may both belong to circuits that implement the arc detection function, that is, in the circuit that implements the arc detection function, the first circuit is a detection circuit, and the third circuit is a self-test circuit for testing the detection circuit.

[0122] Through the above technical solution, a current transformer 302 can realize at least two functions, effectively completing arc detection and communication control of the photovoltaic string 200, reducing the board area occupied by the current transformer 302, saving the internal space of the photovoltaic inverter 300, low cost, easy to produce and process, and strong manufacturability.

[0123] The current transformer 302 is usually located near the photovoltaic inverter 300 for connecting the power cable 204 (see auxiliary reference). Figure 1 ) cable interface, for example, the positive electrode interface (one or more) and the negative electrode interface (one or more) of the photovoltaic inverter 300. In order to make the result of DC arc detection more accurate, in one example, referring to Figure 4 and Figure 5 The windings also include a second primary winding 22. The first primary winding 21 is electrically connected to the positive terminal (PV+) of at least one photovoltaic string 200, and the second primary winding 22 is electrically connected to the negative terminal (PV-) of at least one photovoltaic string 200. When current flows through the first and second primary windings 21 and 22, current is induced in the first and second secondary windings 31 and 32 through the magnetic core 1. This allows the current at the positive and negative terminals of the photovoltaic inverter 300 to undergo AFCI testing before being filtered or passed through other devices. This results in more accurate DC arc detection.

[0124] exist Figure 4 and Figure 5 In the example shown, the second primary winding 22 is entirely wound around the first winding hole 101. In other examples, a portion of the second primary winding 22 is wound around the first winding hole 101, and another portion is wound around other locations of the magnetic core 1. For example, in an example where the magnetic core 1 further includes other winding holes, the second primary winding 22 is wound around both the first winding hole 101 and the other winding hole(s).

[0125] In one example, returning a reference Figure 1 There are multiple photovoltaic strings 200 in the photovoltaic system 100, and each photovoltaic string 200 inputs current to the photovoltaic inverter 300. Figure 4 and Figure 5 The first primary winding 21 may include a plurality of first coils 211 that are not connected to each other. The plurality of first coils 211 are arranged side by side and at intervals. The two ends of each first coil 211 are respectively electrically connected to the circuit board 301. Each first coil 211 is electrically connected to the positive end of a group of photovoltaic strings 200. That is, the plurality of first coils 211 are respectively electrically connected to the PV+ of multiple photovoltaic strings 200.

[0126] In order to reduce the volume of the primary winding, Figure 4 and Figure 5 In the example provided, the second primary winding 22 can combine multiple paths into one. That is, the second primary winding 22 can be a single coil (second coil 220), which is electrically connected to the negative terminals of multiple photovoltaic modules 201. The cross-sectional area of the second coil 220 is larger than that of a single first coil 211. When current is applied, the sum of the currents flowing through the multiple first coils 211 is equal to the current flowing through the second coil 220. Furthermore, this design is more compatible with the routing requirements of the circuit board 301.

[0127] In addition, in some examples, the portion of the second coil 220 wound around the first winding hole 101 may be disposed in the middle of the first winding hole 101, as shown in FIG. Figure 5 , the second coil 220 is located in the middle of the first winding hole 101. At least one first coil 211 is provided on each side of the portion where the second coil 220 is wound around the first winding hole, that is, a first coil 211 can be provided on each side of the second coil 220 ( Figure 5 In the example shown, one first coil 211 may be provided on one side of the second coil 220 and multiple first coils 211 may be provided on the other side, or multiple first coils 211 may be provided on both sides of the second coil 220.

[0128] The two first coils 211 adjacent to the portion where the second coil 220 is wound around the first winding hole 101 are equidistant from the portion where the second coil 220 is wound around the first winding hole 101 . Figure 6The following example illustrates how the distance between the second coil 220 and the first coil 211 is measured. S1 represents the distance from the first coil 211 to the second coil 220 on one side, which is the minimum distance between the side of the first coil 211 facing the second coil 220 and the side of the second coil 220 facing the first coil 211 on that side. S2 represents the distance from the first coil 211 to the second coil 220 on the other side, which is the minimum distance between the side of the first coil 211 facing the second coil 220 and the side of the second coil 220 facing the first coil 211 on that side.

[0129] The aforementioned equal distances are only the desired equalities during the initial design. After the current transformer 302 is actually used in the product, an error is allowed when measuring the distances S1 and S2. For example, the measurement error is allowed to be within ±10 mm, that is, the distances S1 and S2 are considered equal if the size difference is 10 mm or less.

[0130] Designing the coil of the winding close to the middle of the winding hole can reduce leakage magnetic flux, and the second coil 220 can be set in the middle position of the first winding hole 101 in the part of the first winding hole 101. In addition, in order to reduce the leakage magnetic flux of the first coil 211, multiple first coils 211 are set as close as possible to the middle of the first winding hole 101, and multiple first coils 211 can be distributed on both sides of the part of the second coil 110 set in the first winding hole 101, and as close as possible to the second coil 220. However, there is a distance requirement between the first coil 211 and the second coil 220. Then, when the minimum spacing is met (the minimum size allowed for S1 and S2), the distance from the first coil 211 to the second coil 220 on both sides is the same, or a symmetrical design is adopted. In this way, leakage inductance can be reduced, which also reduces the impact on the accuracy of the detection signal amplitude.

[0131] In other examples, when there are multiple groups of photovoltaic strings 200 in the photovoltaic system 100, the second primary winding 22 may also include multiple coils, which correspond to multiple first coils 211 respectively, and each coil of the second primary winding 22 is electrically connected to the negative end of a group of photovoltaic strings 200.

[0132] In other examples, when there is only one set of photovoltaic strings 200 in the photovoltaic system 100, the first primary winding 21 includes only one coil, which is electrically connected to the positive end of the photovoltaic component 201, and the second primary winding 22 includes a second coil 220, which is electrically connected to the negative end of the photovoltaic component 201.

[0133] Figure 7 A schematic diagram of a current transformer 302 of the present application is shown as an example, where "Ts" refers to the number of turns of a coil or winding, for example, 2Ts means 2 turns. Figure 7N1 (2Ts) and N3 (2Ts) are two first coils 211, N2 (2Ts) is the second coil 220 of the second primary winding 22, N4 (4Ts) is a winding electrically connected to the second circuit (for example, the second secondary winding 32), N5 (450Ts) is a winding electrically connected to the first circuit (for example, the first secondary winding 31), and N6 (18Ts) is the third secondary winding 33.

[0134] The number of turns in the arc detection winding is related to the required inductance and detection signal accuracy for AFCI detection. For example, a winding with more turns for sampling arc signals has a higher inductance and a stronger signal coupled to the winding, which improves sampling accuracy and makes arc detection more accurate. Furthermore, the current transformer 302 must also be designed to meet DC bias characteristics and resist DC bias.

[0135] Common-mode current is an inherent characteristic of photovoltaic systems. High-frequency common-mode current not only increases system losses and generates grid-connected current harmonics, but also causes electromagnetic interference and other problems, and can even threaten personal safety. To suppress common-mode current, in the example where the magnetic core 1 includes a first winding hole 101, a first primary winding 21 and at least a portion of a second primary winding 22 are wound around the first winding hole 101. After current is applied, when differential-mode current is conducted between the first and second primary windings 21, 22, the portion of the second primary winding 22 wound around the first winding hole 101 generates magnetic flux in the magnetic core 1 in the same direction as the magnetic flux generated by the first primary winding 21 in the magnetic core 1. Figure 8 An exemplary current flow direction is shown. In this example, the first primary winding 21 and the second primary winding 22 are both wound around the first winding hole 101, wherein: Figure 8 The dotted arrows in the lower middle indicate the flow directions of the currents flowing through different coils (or windings), and the flow directions are merely examples rather than limitations of the present application.

[0136] Reference Figure 8 In the example where the first primary winding 21 includes multiple first coils 211, the current flowing through the first coil 211 flows into one end on the inner side of the first coil 211 in the drawing and flows out from one end on the outer side of the first coil 211; the current flowing through the second primary winding 22 flows into one end on the outer side of the second primary winding 22 in the drawing and flows out from one end on the inner side of the second coil 220. Figure 9 The example shows Figure 8As shown in the figure (dashed arrows in the box), the magnetic paths of the first and second primary windings 21, 22 on the magnetic core 1 have the same direction based on the current direction and winding method of the first and second primary windings 21, 22. That is, after current is applied, when the first and second primary windings 21, 22 conduct differential-mode current, the magnetic flux generated on the magnetic core 1 by the portion of the second primary winding 22 wound around the first winding hole 101 has the same direction as the magnetic flux generated on the magnetic core 1 by the first primary winding 21.

[0137] In this way, when the common mode current flows through the first primary winding 21 and the second primary winding 22, that is, when the first primary winding 21 and the second primary winding 22 conduct the common mode current, magnetic fluxes in opposite directions are generated in the magnetic core 1. Figure 10 The flow direction of the common mode current in the first primary winding 21 and the second primary winding 22 is shown as an example. Figure 11 The magnetic circuit on the magnetic core 1 when the common mode current flows is shown as an example (two dashed boxes with arrows), wherein: Figure 11 The magnetic circuit direction of the outer ring of the two magnetic circuit directions is the direction of the magnetic flux generated on the magnetic core 1 when the common mode current flows through the second primary winding 22. Figure 11 Of the two magnetic circuit directions, the magnetic circuit direction of the inner circle is the direction of magnetic flux generated on the magnetic core 1 when a common mode current flows through the first primary winding 21 .

[0138] Depend on Figure 10 and Figure 11 It can be seen that when the common-mode current flows through the first primary winding 21 and the second primary winding 22, the two generate magnetic fluxes in opposite directions on the magnetic core 1, which can at least partially cancel each other out, thereby suppressing the common-mode current, reducing the possibility of the common-mode current interfering with other devices, and improving the electromagnetic compatibility (EMC) of the system.

[0139] In addition, return reference Figure 6In the example where the first primary winding 21 includes multiple first coils 211, the multiple first coils 211 have the same number of turns, and the number of turns of the second coil 220 wound around the first winding hole 101 is equal to the number of turns of each first coil 211. When a common-mode current flows through the first and second primary windings 21 and 22, magnetic fluxes with opposite directions are generated on the magnetic core 1. When the number of turns of the second coil 220 at the first winding hole 101 is equal to the number of turns of the single first coil 211, the common-mode current flowing through the first and second primary windings 21 and 22 generates magnetic fluxes of equal magnitude on the magnetic core 1. This allows the magnetic flux generated by the common-mode current on the magnetic core 1 to be more offset, further reducing the possibility of the common-mode current interfering with other devices.

[0140] The primary winding and the secondary winding can be wound at any suitable position. In order to facilitate the connection of the winding to the circuit board 301 (for example, welding), return to the reference Figure 4 and Figure 5 The primary winding and the secondary winding can be arranged on the same side of the magnetic core 1 (the side close to the circuit board 301). For example, the fourth magnetic column 14 is located on the side of the first magnetic column 11 facing the circuit board 301, and the first primary winding 21, the second primary winding 22, the first secondary winding 31, the second secondary winding 32, and the third partial winding 33 are all wound on the fourth magnetic column 14. In addition, the primary winding can be wound around the periphery of the secondary winding.

[0141] Reference Figure 5 The current transformer 302 further includes a first insulating sleeve 4 sleeved on the magnetic core 1. The first insulating sleeve 4 passes through the first winding hole 101 and is sleeved on the fourth magnetic column 14. The first secondary winding 31, the second secondary winding 32 and the third secondary winding 33 are all wound outside the first insulating sleeve 4. The primary winding is wound around the periphery of the corresponding secondary winding, for example, referring to Figure 5 The first primary winding 21 and the second primary winding 22 are both wound around the first secondary winding 31 , the second secondary winding 32 and the third secondary winding 33 .

[0142] In addition, in order to insulate the primary winding from the secondary winding, refer back to Figure 4 An insulating tape 7 can be set between the primary winding and the corresponding secondary winding. After the first secondary winding 31, the second secondary winding 32 and the third secondary winding 33 are wound, the insulating tape 7 is first wrapped, and then the first primary winding 21 and the second primary winding 22 are wound.

[0143] The present application does not impose any specific restrictions on the winding sequence of the primary winding and the secondary winding and the assembly steps of the current transformer 302 .

[0144] There are many secondary windings wound on the first insulating sleeve 4. The turns of the first secondary winding 31, the turns of the second secondary winding 32 and the turns of the third secondary winding 33 all have distributed capacitance. In order to reduce the distributed capacitance, a separated structure can be used in the first insulating sleeve 4. For example, referring to Figure 5 A plurality of mutually separated grooves 41 are provided on the first insulating sleeve 4, and the first secondary winding 31, the second secondary winding 32 and the third secondary winding 33 are wound in the plurality of grooves 41, thereby reducing the distributed capacitance of the first secondary winding 31, the second secondary winding 32 and the third secondary winding 33.

[0145] In order to protect the circuit board 301, the current sampled by the current transformer 302 is small (the large current on the primary side is converted into a small current on the secondary side), so the secondary winding is thinner. In order to facilitate the connection between the secondary winding and the circuit board 301, a plurality of pins 6 can be provided on the first insulating sleeve 4. For example, referring to Figure 4 Six pins 6 are provided on the first insulating sleeve 4, the two ends of the first secondary winding 31 are connected to two of the pins 6 on the first insulating sleeve 4, the two ends of the second secondary winding 32 are connected to the other two pins 6 on the first insulating sleeve 4, and the two ends of the third secondary winding 33 are connected to the remaining two pins 6 on the first insulating sleeve 4.

[0146] Reference Figure 4 The primary winding is relatively thick, and both ends of the first primary winding 21 and the second primary winding 22 can be directly welded to the circuit board 301 .

[0147] In addition, in order to support the magnetic core 1, refer to Figure 4 The current transformer 302 may further include an insulating bracket 8, which is arranged on the circuit board 301. A support block 81 (one or more) is provided on the insulating bracket 8. The support block 81 supports the magnetic core 1 so that there is a gap between the magnetic core 1 and the insulating bracket 8, which is convenient for winding the coil or winding. A plurality of through openings 82 are provided on the insulating bracket 8, and the two ends of the first primary winding 21 and the two ends of the second primary winding 22 respectively pass through the corresponding through openings 82. A plurality of pins 6 also respectively pass through the corresponding through holes, so that the ends of the pins 6 and the primary windings extend to the bottom of the insulating bracket 8, which is convenient for connection with the circuit board 301.

[0148] The first insulating sleeve 4 can also be connected to the insulating bracket 8. For example, the first insulating sleeve 4 can be plugged into the insulating bracket 8. Figure 4 and Figure 5 The first insulating sleeve 4 is provided with at least one first pin 42, and the insulating bracket 8 is provided with a corresponding number of sockets 83. The first pins 42 are respectively plugged into the corresponding sockets 83 to prevent the first insulating sleeve 4 from moving at will.

[0149] The present application embodiment also provides another current transformer 302, referring to Figure 12 , Figure 12 The structure of another current transformer 302 is exemplarily shown, wherein the exemplary current transformer 302 includes a magnetic core 1 and a winding, wherein the winding is wound on the magnetic core 1. The magnetic core 1 includes a first winding hole 101 and a second winding hole 102, and a center column 15 located between the first winding hole 101 and the second winding hole 102.

[0150] Figure 13 The structures of various magnetic cores 1 are shown as examples. Figure 13 The magnetic core 1 includes a first magnetic pillar 11, a second magnetic pillar 12, a third magnetic pillar 13, a middle pillar 15, and a fourth magnetic pillar 14. The first magnetic pillar 11 and the fourth magnetic pillar 14 extend in parallel. The second magnetic pillar 12, the third magnetic pillar 13, and the middle pillar 15 are all located between the first magnetic pillar 11 and the fourth magnetic pillar 14. The second magnetic pillar 12 and the third magnetic pillar 13 are distributed along the extension direction of the first magnetic pillar 11. In this example, the second magnetic pillar 12 and the third magnetic pillar 13 can be located at both ends of the first magnetic pillar 11, the middle pillar 15 is located between the second magnetic pillar 12 and the third magnetic pillar 13, and the fourth magnetic pillar 14 extends from the second magnetic pillar 12 to the third magnetic pillar 13. The first winding hole 101 is located between the second magnetic pillar 12 and the middle pillar 15, and the second winding hole 102 is located between the third magnetic pillar 13 and the middle pillar 15.

[0151] Figure 13 In the examples indicated by (a), (b), (c) and (d), the magnetic pillar above the dotted line L1 is the first magnetic pillar 11, the magnetic pillar below the dotted line L2 is the fourth magnetic pillar 14, and among the three magnetic pillars between the dotted lines L1 and L2, the magnetic pillar on the far right is the second magnetic pillar 12, the magnetic pillar on the far left is the third magnetic pillar 13, and the magnetic pillar in the middle is the middle pillar 15. The first winding hole 101 and the second winding hole 102 are distributed along the extension direction of the first magnetic pillar 11.

[0152] Reference Figure 13 The magnetic core 1 is provided with at least one air gap 103 on both sides of the middle column 15, that is, at least two air gaps 103 are provided on the magnetic core 1, and at least one air gap 103 is provided on any side of the middle column 15.

[0153] Figure 13In the magnetic core 1 (EI type) shown in (a), the second magnetic leg 12, the third magnetic leg 13, and the center leg 15 are all connected to the same side of the first magnetic leg 11. The center leg 15 contacts the fourth magnetic leg 14. Air gaps 103 are formed between the second magnetic leg 12 and the third magnetic leg 13 and the fourth magnetic leg 14. In other words, the magnetic core 1 is provided with two air gaps 103, located on different sides of the center leg 15. The two air gaps 103 are a first air gap 1031 and a second air gap 1032. The first air gap 1031 is formed between the second magnetic leg 12 and the fourth magnetic leg 14, and the second air gap 1032 is formed between the third magnetic leg 13 and the fourth magnetic leg 14.

[0154] Figure 13 In the magnetic core 1 (OC type) shown in (b), air gaps 103 are provided on the first magnetic column 11, the second magnetic column 12 and the fourth magnetic column 14, wherein the air gaps 103 on the first magnetic column 11 and the fourth magnetic column 14 (one of which is the first air gap 1031) are provided on the right side of the middle column 15, and the air gap 103 on the third magnetic column 13 (the second air gap 1032) is provided on the left side of the middle column 15, and air gaps 103 are provided on both sides of the middle column 15.

[0155] Figure 13 In the magnetic core 1 (CIC type) shown in (c), two air gaps 103 are respectively provided on the first magnetic column 11 and the fourth magnetic column 14, wherein the two air gaps 103 on the first magnetic column 11 are respectively located on different sides of the middle column 15, and the two air gaps 103 on the fourth magnetic column 14 are respectively located on different sides of the middle column 15, and two air gaps 103 are respectively provided on both sides of the middle column 15. Among them, the air gap 103 on the left side of the middle column 15 on the first magnetic column 11 can be the second air gap 1032, and the air gap 103 on the right side of the middle column 15 can be the first air gap 1031; it can also be that the air gap 103 on the left side of the middle column 15 on the fourth magnetic column 14 is the second air gap 1032, and the air gap 103 on the right side of the middle column 15 is the first air gap 1031; it can also be that the air gap 103 on the left side of the middle column 15 on the first magnetic column 11 is the second air gap 1032, and the air gap 103 on the right side of the middle column 15 on the fourth magnetic column 14 is the first air gap 1031.

[0156] Figure 13 In the magnetic core 1 (double E-type) shown in (d), a first air gap 1031 is provided on the second magnetic pillar 12, and a second air gap 1032 is provided on the third magnetic pillar 13. The two air gaps 103 are located on different sides of the center pillar 15. The center pillar 15 may include a first sub-pillar and a second sub-pillar. The first sub-pillar is connected to the first magnetic pillar 11, and the second sub-pillar is connected to the fourth magnetic pillar 14. The end of the first sub-pillar facing away from the first magnetic pillar 11 contacts the end of the second sub-pillar facing away from the fourth magnetic pillar 14. In other words, in this example, the center pillar 15 may be formed by splicing two sub-pillars (the first sub-pillar and the second sub-pillar).

[0157] It should be noted that the above-mentioned “up”, “down”, “left” and “right” are merely reference directions on the drawings, intended to facilitate explanation, and are not limitations of this application.

[0158] In addition, the first winding hole 101 and the second winding hole 102 are both through-hole-shaped spatial structures formed on the magnetic core 1. The sizes of the first winding hole 101 and the second winding hole 102 can be set according to the winding situation, and this application does not impose any specific restrictions on this.

[0159] Air gaps 103 are set on both sides of the center column 15. The magnetic resistance of the air gap 103 is large, and the magnetic circuit will be closed at the center column 15 first. Figure 13 Taking the magnetic core 1 shown in (a) as an example, when the two windings are wound through the first winding hole 101 and the second winding hole 102 respectively, the winding passing through the first winding hole 101 is located between the second magnetic column 12 and the middle column 15, and the winding passing through the second winding hole 102 is located between the third magnetic column 13 and the middle column 15. The two windings form two magnetic circuits respectively. Figure 14 , Figure 14 The case of two magnetic circuits (a first magnetic circuit and a second magnetic circuit) is shown as an example.

[0160] Reference Figure 14 Since there is no air gap 103 at the center column 15 and the magnetic resistance is small, the two magnetic circuits will preferentially close at the center column 15. For example, in the first magnetic circuit, since there is a second air gap 1032 between the third magnetic column 13 and the fourth magnetic column 14, the first magnetic circuit will preferentially close at the center column 15 compared to closing at the third magnetic column 13. For another example, in the second magnetic circuit, since there is a first air gap 1031 between the second magnetic column 12 and the fourth magnetic column 14, the second magnetic circuit will preferentially close at the center column 15 compared to closing at the second magnetic column 12. This achieves mutual decoupling of the first and second magnetic circuits, reducing the possibility of mutual interference between the first and second magnetic circuits.

[0161] The structure of the magnetic core 1 of the present application can be selected in a variety of ways. The magnetic core 1 can be a spliced structure, for example, an E-type magnetic core and an I-type magnetic core, or a double E-type magnetic core, which is conducive to adjusting the magnetic inductance and other properties. The material of the magnetic core 1 can also be any suitable material, for example, manganese-zinc ferrite, nickel-zinc ferrite, etc.

[0162] The windings of the current transformer 302 may include a primary winding and a secondary winding. The current on the primary winding may be coupled to the secondary winding through the magnetic core 1 .

[0163] Reference Figure 15 , Figure 15The primary winding on the magnetic core 1 is shown as an example. The primary winding may include a first primary winding 21 and a second primary winding 22 wound on the magnetic core 1. The first primary winding 21 passes through the first winding hole 101, and part of the second primary winding 22 passes through the second winding hole 102. Figure 16 , Figure 16 A secondary winding on a magnetic core 1 is shown as an example. The secondary winding may include a first secondary winding 31 and a second secondary winding 32 wound on the magnetic core 1. The first secondary winding 31 passes through a first winding hole 101, and the second secondary winding 32 passes through a second winding hole 102.

[0164] The first primary winding 21 and the first secondary winding 31 both pass through the first winding hole 101. That is, the first primary winding 21 and the first secondary winding 31 correspond to each other. When current flows through the first primary winding 21, current is induced in the first secondary winding 31 through the magnetic core 1. The portion of the second primary winding 22 that passes through the second winding hole 102 corresponds to the second secondary winding 32. When current flows through the second primary winding 22, current is induced in the second secondary winding 32 through the magnetic core 1.

[0165] One of the first secondary winding 31 and the second secondary winding 32 is electrically connected to a first circuit for DC arc detection, and the other is electrically connected to a second circuit for power line carrier communication. For example, the first secondary winding 31 is electrically connected to the first circuit, and the second secondary winding 32 is electrically connected to the second circuit. For another example, the second secondary winding 32 is electrically connected to the first circuit, and the first secondary winding 31 is electrically connected to the second circuit.

[0166] In addition, in order to detect whether the first circuit for DC arc detection is operating normally, a third circuit (eg, a self-test circuit) for testing the first circuit is also provided on the circuit board 301 to determine whether the function of the first circuit is normal. Figure 16 The secondary winding may further include a third secondary winding 33 wound around the magnetic core 1. The third secondary winding 33 is electrically connected to the third circuit. In the example where the first secondary winding 31 is electrically connected to the first circuit for DC arc detection, both the third secondary winding 33 and the first secondary winding 31 pass through the first winding hole 101.

[0167] When current flows through the first primary winding 21, the third secondary winding 33 feeds the induced current back to the third circuit to test the proper operation of the first circuit for DC arc detection. If the first circuit is operating properly, the current induced by the first secondary winding 31 is fed back to the first circuit for analysis, yielding accurate results.

[0168] At least two functions can be achieved through an integrated magnetic core 1, effectively completing arc detection and communication control of the photovoltaic string 200, reducing the board area occupied by the current transformer 302, saving the internal space of the photovoltaic inverter 300, low cost, easy to produce and process, and strong manufacturability.

[0169] Return to reference Figure 14 Air gaps 103 are provided on both sides of the center column 15. Since there is no air gap 103 at the center column 15, the magnetic resistance is relatively small, and the two magnetic circuits generated by the first primary winding 21 and the second primary winding 22 will preferentially close at the center column 15. For example, after current is applied, the first primary winding 21 forms a first magnetic circuit in the magnetic core 1, and the portion of the second primary winding 22 passing through the second winding hole 102 forms a second magnetic circuit in the magnetic core 1. The first magnetic circuit and the second magnetic circuit preferentially close at the center column 15, achieving mutual decoupling of the two magnetic circuits, reducing the possibility of mutual influence and interference between the two magnetic circuits, and enabling the two functions of DC arc detection and power line carrier communication to be performed independently.

[0170] Based on the provision of air gaps 103 on either side of the center leg 15, in order to further preferentially close the magnetic circuit on the center leg 15 and reduce the impedance of the center leg 15, when current is applied, with the first primary winding 21 and the second primary winding 22 conducting differential-mode current, the portion of the second primary winding 22 passing through the second winding hole 102 generates a magnetic flux on the center leg 15 that is opposite in direction to the magnetic flux generated by the first primary winding 21 on the center leg 15. In other words, the magnetic flux directions of the first and second magnetic circuits on the center leg 15 are opposite, resulting in a lower impedance on the center leg 15 (superposition of the magnetic fluxes would generate a higher impedance). This allows the first and second magnetic circuits to preferentially close on the center leg 15, further reducing the possibility of mutual influence and interference between the first and second magnetic circuits.

[0171] It is understandable that the winding method of the first primary winding 21 and the winding direction of the second primary winding 22 can be determined as needed, as long as the magnetic flux directions of the first magnetic circuit and the second magnetic circuit at the center column 15 are opposite.

[0172] The photovoltaic string 200 is equivalent to the input source of the photovoltaic inverter 300. When the current is loaded, the current flowing through the first primary winding 21 is equal to the current flowing through the second primary winding 22. Figure 15 The current at the positive terminal (PV+) of the photovoltaic string 200 will flow to the first primary winding 21, then to the second primary winding 22, and then back to the negative terminal (PV-) of the photovoltaic string 200 to form a loop.

[0173] The presence of common-mode voltage creates parasitic capacitance between the photovoltaic terminals of photovoltaic inverter 300 and the ground. When photovoltaic inverter 300 is powered on, the common-mode voltage creates a loop between photovoltaic strings 200, photovoltaic inverter 300, the grid, and the ground, generating common-mode current. This is an inherent characteristic of photovoltaic system 100. High-frequency common-mode current not only increases system losses and generates grid-connected current harmonics, but also causes electromagnetic interference and other problems, and can even threaten personal safety.

[0174] To suppress common-mode current, a portion of the second primary winding 22 is guided to and wound around the first winding hole 101. When current is applied, and differential-mode current is conducted between the first and second primary windings 21, 22, the portion of the second primary winding 22 passing through the first winding hole 101 and the first primary winding 21 generate magnetic flux in the same direction in the magnetic core 1.

[0175] That is, a portion of the second primary winding 22 passes through the second winding hole 102, and a portion passes through the first winding hole 101. Figure 15 Taking the winding method shown in FIG as an example, the second primary winding 22 includes a second coil, which includes a first portion 221, a second portion 222, and a third portion 223 that are integrally arranged. The first portion 221 is wound around the magnetic core 1 through the second winding hole 102, the third portion 223 is wound around the magnetic core 1 through the first winding hole 101, and the second portion 222 connects the first portion 221 and the third portion 223.

[0176] After the current is loaded, when the common-mode current flows through the third portion 223 and the first primary winding 21, magnetic fluxes of equal magnitude and opposite directions are generated on the magnetic core 1 respectively. The magnetic fluxes generated by the common-mode current on the magnetic core 1 cancel each other out, thereby suppressing the common-mode current, reducing the possibility of interference with other devices, and improving the electromagnetic compatibility (EMC) of the system.

[0177] Return to reference Figure 1 There are multiple photovoltaic strings 200 in the photovoltaic system 100, and each photovoltaic string 200 inputs current to the photovoltaic inverter 300. Figure 12 The first primary winding 21 includes a plurality of first coils 211 that are not connected to each other. The plurality of first coils 211 are arranged side by side and at intervals. The two ends of each first coil 211 are electrically connected to the circuit board 301 respectively. Each first coil 211 is electrically connected to the positive end of a group of photovoltaic strings 200 (the plurality of first coils 211 correspond to multiple PV+ channels respectively).

[0178] In other examples, the second primary winding 22 may also include multiple coils, each corresponding to the multiple first coils 211. However, to reduce the volume of the primary winding, the second primary winding 22 may combine multiple coils into one coil. That is, the second primary winding 22 may be a single coil (the second coil). The cross-sectional area of the second coil is larger than the cross-sectional area of the single first coil 211. When current is applied, the sum of the currents flowing through the multiple first coils 211 is equal to the current flowing through the second coil.

[0179] In other examples, the second primary winding 22 may also entirely pass through the second winding hole 102 , that is, the second primary winding 22 is entirely wound at the second winding hole 102 .

[0180] The primary winding and the secondary winding can be wound at any suitable position. In order to facilitate the connection of the winding to the circuit board 301 (for example, welding), refer to Figure 12 The primary winding and the secondary winding can be arranged on the same side of the magnetic core 1 (the side close to the circuit board 301).

[0181] For example, the fourth magnetic column 14 is located on the side of the first magnetic column 11 facing the circuit board 301, referring to Figure 15 The first primary winding 21 and the second primary winding 22 are both wound on the fourth magnetic column 14. The first primary winding 21 is located between the second magnetic column 12 and the middle column 15. The portion of the second primary winding 22 passing through the second winding hole 102 is located between the third magnetic column 13 and the middle column 15. The portion of the second primary winding 22 passing through the first winding hole 101 is located between the second magnetic column 12 and the middle column 15. Figure 16 The first secondary winding 31, the second secondary winding 32 and the third secondary winding 33 are all wound on the fourth magnetic column 14. The first secondary winding 31 and the third secondary winding 33 are located between the second magnetic column 12 and the middle column 15, and the second secondary winding 32 is located between the third magnetic column 13 and the middle column 15.

[0182] Figure 15 and Figure 16 by Figure 13 Taking the magnetic core 1 shown in (a) as an example, in other examples, the winding can also be wound around Figure 13 In the examples (b), (c) and (d), the primary winding and the secondary winding may be wound on different magnetic columns.

[0183] When the primary winding and the corresponding secondary winding are wound on the same magnetic column, the primary winding may be wound around the periphery of the corresponding secondary winding.

[0184] The secondary winding can be wound around the corresponding position of the magnetic core 1 first, for example, refer to Figure 16The current transformer 302 further includes a first insulating sleeve 4 and a second insulating sleeve 5, which are sleeved over the magnetic core 1. The first insulating sleeve 4 passes through the first winding hole 101, and the second insulating sleeve 5 passes through the second winding hole 102. Specifically, the first insulating sleeve 4 is positioned between the second magnetic column 12 and the center column 15, and the second insulating sleeve 5 is positioned between the third magnetic column 13 and the center column 15. The first secondary winding 31 and the third secondary winding 33 are wound outside the first insulating sleeve 4, and the second secondary winding 32 is wound outside the second insulating sleeve 5.

[0185] Then the primary winding is wound around the corresponding secondary winding, for example, refer to Figure 17 , Figure 17 The winding positions of the primary winding and the secondary winding are shown by way of example. The first primary winding 21 is wound around the first secondary winding 31 and the third secondary winding 33. The part of the second primary winding 22 passing through the second winding hole 102 (the first part 221) is wound around the second secondary winding 32. The part of the second primary winding 22 passing through the first winding hole 101 (the third part 223) is wound around the first secondary winding 31 (or the third secondary winding 33).

[0186] In addition, in order to insulate the primary winding from the secondary winding, refer to Figure 18 , Figure 18 The structure of the current transformer 302 is shown in another exemplary embodiment. Insulating tape 7 can be provided between the primary winding and the corresponding secondary winding. After the secondary winding is wound, the insulating tape 7 is wrapped around it before the primary winding is wound. For example, insulating tape 7 is provided between the first primary winding 21 and the first secondary winding 31, and insulating tape 7 is provided between the second primary winding 22 and the second secondary winding 32.

[0187] The present application does not impose any specific restrictions on the winding sequence of the primary winding and the secondary winding and the assembly steps of the current transformer 302 .

[0188] There are many secondary windings wound on the first insulating sleeve 4. The turns of the first secondary winding 31 and the turns of the third secondary winding 33 both have distributed capacitance. In order to reduce the distributed capacitance, a separated structure can be used in the first insulating sleeve 4. For example, return to reference Figure 16 The first insulating sleeve 4 is provided with a plurality of mutually separated grooves 41, and the first secondary winding 31 and the third secondary winding 33 are wound in the plurality of grooves 41, thereby reducing the distributed capacitance of the first secondary winding 31 and the third secondary winding 33. Furthermore, the second insulating sleeve 5 may also adopt the aforementioned separated structure.

[0189] In order to protect the circuit board 301, the current sampled by the current transformer 302 is small (the large current on the primary side is converted into a small current on the secondary side), so the secondary winding is thinner. In order to facilitate the connection between the secondary winding and the circuit board 301, pins 6 can be provided on the first insulating sleeve 4 and the second insulating sleeve 5. For example, referring to Figure 16 Four pins 6 are provided on the first insulating sleeve 4, the two ends of the first secondary winding 31 are connected to two of the pins 6 on the first insulating sleeve 4, and the two ends of the third secondary winding 33 are connected to the other two pins 6 on the first insulating sleeve 4; two pins 6 are provided on the second insulating sleeve 5, and the two ends of the second secondary winding 32 are connected to the two pins 6 on the second insulator.

[0190] Reference Figure 17 The primary winding is relatively thick, and both ends of the first primary winding 21 and the second primary winding 22 can be directly welded to the circuit board 301 .

[0191] In addition, in order to support the magnetic core 1, refer to Figure 18 The current transformer 302 may further include an insulating bracket 8, which is arranged on the circuit board 301. A support block 81 is provided on the insulating bracket 8, which supports the magnetic core 1 so that there is a gap between the magnetic core 1 and the insulating bracket 8. A plurality of through openings 82 are provided on the insulating bracket 8, and the two ends of the first primary winding 21 and the two ends of the second primary winding 22 respectively pass through the corresponding through openings 82. A plurality of pins 6 also respectively pass through the corresponding through holes, so that the ends of the pins 6 and the primary windings extend to the bottom of the insulating bracket 8, which is convenient for connection with the circuit board 301.

[0192] The first insulating sleeve 4 and the second insulating sleeve 5 can also be connected to the insulating bracket 8. For example, the first insulating sleeve 4 and the second insulating sleeve 5 can be plugged into the insulating bracket 8. Figure 16 The first insulating sleeve 4 is provided with at least one first pin 42 ( Figure 16 The second insulating sleeve 5 is provided with a plurality of second pins 51 ( Figure 16 An example of two second pins 51 is shown in FIG. Figure 18 The insulating bracket 8 is provided with a plurality of sockets 83 , and the first pin 42 and the second pin 51 are respectively plugged into the corresponding sockets 83 to prevent the first insulating sleeve 4 and the second insulating sleeve 5 from moving freely.

[0193] Figure 19An exemplary schematic diagram of the current transformer 302 of the present application is shown. In the figure, N1 (1Ts), N2 (1Ts), and N3 (1Ts) are respectively the three first coils 211 of the first primary winding 21, and N4 is the second primary winding. The portion of N4 passing through the first winding hole 101 is wound one turn (1ts), and the portion of N4 passing through the second winding hole 102 is wound two turns (2ts). N6 (300Ts) is the first secondary winding 31, N7 (12Ts) is the third secondary winding 33, and N5 (2Ts) is the second secondary winding 32. The number of winding turns for sampling arc signals is relatively large. The more turns, the greater the inductance, and the stronger the signal coupled to the winding, which can improve the sampling accuracy and make the arc detection result more accurate.

[0194] In addition, the current transformer 302 of the present application may also be an integration of three or more current transformers, for example, referring to Figure 20 , Figure 20 The magnetic core 1 of another current transformer 302 provided in the present application is shown as an example. The magnetic core 1 includes a first magnetic column 11, a second magnetic column 12, a third magnetic column 13, a fourth magnetic column 14, and two center columns 15. The first magnetic column 11 and the fourth magnetic column 14 extend in parallel. The second magnetic column 12, the third magnetic column 13, and the two center columns 15 are located between the first magnetic column 11 and the fourth magnetic column 14. The second magnetic column 12 and the third magnetic column 13 are located at both ends of the first magnetic column 11 in the extension direction. The two center columns 15 are located between the second magnetic column 12 and the third magnetic column 13. The fourth magnetic column 14 extends from the second magnetic column 12 to the third magnetic column 13. Air gaps 103 are provided on both sides of each center column 15, so that the first magnetic circuit, the second magnetic circuit, and the third magnetic circuit are preferentially closed at the two center columns 15.

[0195] In other examples, the photovoltaic inverter 300 may further include other circuits in addition to the DC arc detection circuit and the PLC circuit. These other circuits may be disposed on the circuit board 301. The first secondary winding 31 and the second secondary winding 32 may not be electrically connected to the DC arc detection circuit and the PLC circuit. Instead, the first secondary winding 31 and the second secondary winding 32 may be electrically connected to other circuits with different functions. In examples including the third secondary winding 33, the third secondary winding 33 may also be electrically connected to a circuit with an independent function.

[0196] In other examples, the current transformer 302 can also be set in other devices, with the first primary winding 21 being used to electrically connect to a power source, and the first secondary winding 31 and the second secondary winding 32 being used to electrically connect to different circuits (circuits that perform different functions). The current induced by the first secondary winding 31 and the current induced by the second secondary winding 32 are fed back to different circuits, respectively. A single magnetic core 1 can achieve at least two functions, reducing the volume and board area of the current transformer 302 and lowering production and manufacturing costs.

[0197] The current transformer 302 of the present application may also be used in other devices, such as power supply equipment.

[0198] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A photovoltaic inverter, characterized in that: include: A circuit board, on which a first circuit for DC arc detection and a second circuit for power line carrier communication are provided; a current transformer, the current transformer being disposed on the circuit board and comprising a magnetic core and a winding wound around the magnetic core; The winding includes a first primary winding, a second primary winding, a first secondary winding and a second secondary winding. The first primary winding is used to be electrically connected to the positive end of at least one group of photovoltaic strings, and the second primary winding is used to be electrically connected to the negative end of the at least one group of photovoltaic strings. Each group of photovoltaic strings includes at least one photovoltaic module; one of the first secondary winding and the second secondary winding is electrically connected to the first circuit, and the other is electrically connected to the second circuit.

2. The photovoltaic inverter according to claim 1, characterized in that: The magnetic core is provided with a first winding hole, and the first primary winding, the second primary winding, the first secondary winding and the second secondary winding are all wound at the first winding hole; When the first primary winding and the second primary winding conduct a common mode current, the magnetic flux generated by the second primary winding on the magnetic core is in a direction opposite to the magnetic flux generated by the first primary winding on the magnetic core.

3. The photovoltaic inverter according to claim 2, characterized in that: The magnetic core includes a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column, The second magnetic pillar and the third magnetic pillar are arranged along the extension direction of the first magnetic pillar, the second magnetic pillar and the third magnetic pillar are located on the same side of the first magnetic pillar, the fourth magnetic pillar is located on the side of the second magnetic pillar away from the first magnetic pillar, the fourth magnetic pillar extends from the second magnetic pillar to the third magnetic pillar, and the first magnetic pillar, the second magnetic pillar, the third magnetic pillar and the fourth magnetic pillar surround the first winding hole.

4. The photovoltaic inverter according to claim 1, characterized in that: The magnetic core includes a first winding hole and a second winding hole, and a center column located between the first winding hole and the second winding hole. A first air gap is provided at other positions of the portion of the magnetic core surrounding the first winding hole except the center column. A second air gap is provided at other positions of the portion of the magnetic core surrounding the second winding hole except the center column. The first primary winding and the first secondary winding are wound around the first winding hole, and the second secondary winding and at least a portion of the second primary winding are wound around the second winding hole.

5. The photovoltaic inverter according to claim 4, characterized in that: When the first primary winding and the second primary winding conduct differential mode current, the magnetic flux generated by the portion of the second primary winding wound in the second winding hole in the center column is opposite in direction to the magnetic flux generated by the first primary winding in the center column.

6. The photovoltaic inverter according to claim 4 or 5, characterized in that: A portion of the second primary winding is wound around the first winding hole, and another portion of the second primary winding is wound around the second winding hole; When the first primary winding and the second primary winding conduct common mode current, the magnetic flux generated by the portion of the second primary winding wound around the first winding hole in the magnetic core is in the opposite direction to the magnetic flux generated by the first primary winding in the magnetic core.

7. The photovoltaic inverter according to any one of claims 4 to 6, characterized in that: A third circuit is provided on the circuit board, and the third circuit is used to test the first circuit; The winding further includes a third secondary winding wound around the first winding hole, the first secondary winding is electrically connected to the first circuit, and the third secondary winding is electrically connected to the third circuit.

8. The photovoltaic inverter according to any one of claims 4 to 7, characterized in that: The magnetic core further comprises: a first magnetic column, a second magnetic column, and a third magnetic column, wherein the second magnetic column and the third magnetic column are arranged along the extension direction of the first magnetic column, and the middle column is located between the second magnetic column and the third magnetic column; A fourth magnetic column, the fourth magnetic column is located on a side of the middle column away from the first magnetic column, the fourth magnetic column extends from the second magnetic column to the third magnetic column, the first winding hole is located between the second magnetic column and the middle column, and the second winding hole is located between the third magnetic column and the middle column.

9. The photovoltaic inverter according to claim 8, characterized in that: The second magnetic column, the third magnetic column, and the middle column are all connected to the same side of the first magnetic column. The middle column is in contact with the fourth magnetic column. The first air gap is formed between the second magnetic column and the fourth magnetic column, and the second air gap is formed between the third magnetic column and the fourth magnetic column.

10. The photovoltaic inverter according to claim 8 or 9, characterized in that: The first primary winding and the second primary winding are both wound on the fourth magnetic column, and the fourth magnetic column is located on a side of the first magnetic column facing the circuit board.

11. The photovoltaic inverter according to any one of claims 4 to 10, characterized in that: The current transformer further includes a first insulating sleeve sleeved on the magnetic core, the first insulating sleeve passing through the first winding hole, the first secondary winding wound outside the first insulating sleeve, the first primary winding wound around the periphery of the first secondary winding, and an insulating tape provided between the first primary winding and the first secondary winding; The current transformer also includes a second insulating sleeve sleeved on the magnetic core, the second insulating sleeve passes through the second winding hole, the second secondary winding is wound outside the second insulating sleeve, the part of the second primary winding passing through the second winding hole is wound around the periphery of the second secondary winding, and an insulating tape is provided between the second primary winding and the second secondary winding.

12. The photovoltaic inverter according to any one of claims 2 to 11, characterized in that: There are multiple groups of photovoltaic strings, the first primary winding includes multiple first coils, the multiple first coils are arranged at intervals, and each first coil is electrically connected to the positive terminal of a corresponding group of photovoltaic strings; The second primary winding includes a second coil, the cross-sectional area of the second coil is larger than the cross-sectional area of a single first coil, and the second coil is used to be electrically connected to the negative terminals of the plurality of photovoltaic strings.

13. The photovoltaic inverter according to claim 12, characterized in that: The plurality of first coils have the same number of turns, and the number of turns of any one of the first coils is equal to the number of turns of the second coil wound around the first winding hole.

14. The photovoltaic inverter according to claim 12 or 13, characterized in that: At least one first coil is provided on each side of the portion where the second coil is wound around the first winding hole; The two first coils adjacent to the portion of the second coil wound in the first winding hole are equidistant from the portion of the second coil wound in the first winding hole.

15. A current transformer, characterized in that: comprising a magnetic core and a winding wound on the magnetic core; The winding includes a first primary winding, a second primary winding, a first secondary winding and a second secondary winding. The first primary winding is used to be electrically connected to the positive terminal of the power supply, the second primary winding is used to be electrically connected to the negative terminal of the power supply, the first secondary winding is used to be electrically connected to the circuit for DC arc detection, and the second secondary winding is used to be electrically connected to the circuit for power line carrier communication.

16. The current transformer according to claim 15, characterized in that: The magnetic core is provided with a first winding hole, and the first primary winding, the second primary winding, the first secondary winding and the second secondary winding are all wound at the first winding hole; When the first primary winding and the second primary winding conduct a common mode current, the magnetic flux generated by the second primary winding on the magnetic core is in a direction opposite to the magnetic flux generated by the first primary winding on the magnetic core.

17. The current transformer according to claim 15, characterized in that: The magnetic core includes a first winding hole and a second winding hole, and a center column located between the first winding hole and the second winding hole. A first air gap is provided at other positions of the portion of the magnetic core surrounding the first winding hole except the center column. A second air gap is provided at other positions of the portion of the magnetic core surrounding the second winding hole except the center column. The first primary winding and the first secondary winding are wound around the first winding hole, and the second secondary winding and at least a portion of the second primary winding are wound around the second winding hole.

18. The current transformer according to claim 17, characterized in that: When the first primary winding and the second primary winding conduct differential mode current, the magnetic flux generated by the portion of the second primary winding wound in the second winding hole in the center column is opposite in direction to the magnetic flux generated by the first primary winding in the center column.

19. The current transformer according to any one of claims 16 to 18, characterized in that: The first primary winding includes a plurality of first coils, and the plurality of first coils are arranged at intervals; The second primary winding includes a second coil, and the cross-sectional area of the second coil is larger than the cross-sectional area of the single first coil; When current is loaded, the sum of currents flowing through the plurality of first coils is equal to the current flowing through the second coil.

20. The current transformer according to claim 19, characterized in that The plurality of first coils have the same number of turns, and the number of turns of the second coil wound around the first winding hole is equal to the number of turns of each of the first coils.

21. A photovoltaic system, characterized in that: comprising at least one optimizer and the photovoltaic inverter according to any one of claims 1 to 14; Each of the optimizers is used to connect to at least one of the photovoltaic components; The at least one optimizer is electrically connected to the second circuit of the photovoltaic inverter.

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